Preheat oven to 350 degrees F. Butter and flour Bundt pan; set aside.

Whisk flour, baking powder, and salt in a medium bowl.

Combine sugar and orange zest in a large bowl; using your fingertips, rub together until orange sugar is well blended.

Add 1 cup butter to orange sugar. Using an electric mixer on high speed, beat until mixture is light and fluffy, about 4 minutes.

Add eggs one at a time, beating between additions and occasionally scraping down sides of bowl with a rubber spatula.

Beat until mixture is light and fluffy, about 4 minutes longer.

Reduce speed to low. Add dry ingredients in 3 additions, alternating with buttermilk in 2 additions, beginning and ending with dry ingredients.

Pour batter into prepared Bundt pan.

Bake cake until golden brown, about 60-70 minutes.

Transfer to wire rack and let cake cool in pan for 20 minutes.

Invert cake onto rack; remove pan and let cake cool completely.

While the cake is cooling, begin to prepare the glaze.

Combine orange marmalade, orange juice and lemon juice in a small saucepan. Bring to a boil, reduce heat, and simmer, stirring occasionally, until glaze is reduced to 1/2 cup, 8-10 minutes.

Strain glaze into a small bowl, discard solids in strainer.

Pour glaze over completely cooled cake and let sit for 10 minutes before serving.